'Cementing' wells tied to oil rig blowouts

'Cementing' of rig's well eyed as possible culprit in blowout

ERIC NALDER, HOUSTON CHRONICLE |
April 28, 2010

Investigators with the U.S. Minerals Management Service raised concerns three years ago about oil rig blowouts associated with cementing wells, noting that accidents were continuing with regularity, most in the Gulf of Mexico.

Though the cause of last week's explosion on the Deepwater Horizon remains under investigation, officials with Transocean have said a blowout within the deep oil well was likely to blame for the deadly blast. At the time of the accident, crews were ï¿½cementing,ï¿½ or installing casing to secure the walls of the well.

A 2007 MMS study found that although blowouts with offshore drilling operations were becoming less frequent, less deadly and less polluting, cementing-associated troubles persisted.

Cementing problems were associated with 18 of 39 blowouts between 1992 and 2006, and 18 of 70 from 1971 to 1991. There were 17 blowouts in the earlier period where contributing factors weren't identified.

Nearly all the blowouts examined occurred in the Gulf of Mexico.

ï¿½During the current period (1992 to 2006), the percentage of blowouts associated with cementing operations increased significantly from the previous period,ï¿½ said the study.

Change slow in coming

The MMS and the American Petroleum Institute were tasked with developing new standards for ï¿½best cementing practicesï¿½ for offshore oil and gas operations.

API standards are voluntary but can become mandatory when adopted in federal regulations.

The work, in the making for nearly four years, isn't completed.

ï¿½Sometime soon,ï¿½ said Andy Radford, senior policy adviser on offshore issues for the API. ï¿½It proved to be a little more challenging that anticipated.

ï¿½There are so many different ways to drill a well, and cement a well,ï¿½ said Radford, adding that they had to ï¿½reconcileï¿½ a lot of company practices.

Timor Sea blowout

In a different hemisphere last August, another oil rig blowout sent thousands of barrels of oil spilling into the Timor Sea near Indonesia and East Timor. The culprit: a problem during cementing, which is supposed to keep gases and oil from shooting skyward and exploding into fire.

That accident and the blast on the Deepwater Horizon had at least one circumstance in common.

Both happened in a transition period when the offshore oil wells were being capped off and the gaps around drilling casings were being cemented shut to prevent pressurized gases and oil from escaping.

Much more is known about the Timor Sea incident; a commission appointed by the Australian government has turned up solid evidence it was caused by a mistake during careless cementing operations.

Accidents similar

Elmer ï¿½Budï¿½ Danenberger, the engineer who oversaw American investigations of offshore drilling accidents until he retired in January, sees a likely similarity between the two accidents ï¿½ the fact that cementing was going on ï¿½ though other circumstances were different.

Danenberger, who coauthored the MMS 2007 study, said another ï¿½big ticket itemï¿½ in the investigation of the Gulf of Mexico blowout will be the failure of backup systems.

Among the big questions: Why didn't a blowout preventer work and stop the gusher of hot oil and gas that exploded when it reached the platform?

ï¿½That's how they are designed,ï¿½ he said.

In the Timor Sea incident, oil leaked for 10 weeks, and slicks moved as far as 200 miles from the spill site, said John Amos, a former oil exploration geologist whose organization, SkyTruth, tracks oil spills through satellite images.